One of the main sources of atmospheric pollutants today is from coal-fired electrical utility boilers. In these installations, a clean fossil fuel, such as natural gas, is not a practical substitute for coal in the generation of electricity because of scarcity and cost. Furthermore, the available supply of clean fuel may combat pollution more effectively when used to fulfill residential and small commercial needs.
During conventional coal burning or gasification process, when the temperature is above the coal's softening point, plastic properties of coal start to develop. Upon reaching this point, generally between about 370° C. and about 480° C., the coal particles begin to swell and deform due to the formation of bubbles during devolatilization. As the temperature increases, deformation becomes more severe, the coal becomes plastic and sticky, and may eventually become thin films surrounding the incompletely burning small particles. At this stage, the coal is considered incompletely gasified. The coal may then break into small tiny fine solid carbon particles and emit into the air like “black smog.” The particles are solid, toxic and seriously carcinogenic, so when a great amount of the black solid carbon particles are emitted into the air, not only the environment is polluted, but the human health is seriously harmed. Therefore, there remains a need for a new and improved coal gasified process to avoid producing the harmful substances likewise “black solid smog” in the exhausted gas and make the coal completely gasify and to burn completely, and released less carbon dioxide to overcome the problems stated above.